9-Hydroxy-undeca-4,10-dien-1-al was first isolated as an unwanted by-product of an attempted double Claisen type reaction designed primarily to give the diene aldehyde of formula EQU OHC--(CH.sub.2).sub.2 --CH.dbd.CH--(CH.sub.2).sub.3 --CH.dbd.CH--(CH.sub.2).sub.2 --CHO
a key intermediate for the synthesis of macrocyclic derivatives [see copending application Ser. No. 76,960].
We have surprisingly discovered that the isolated hydroxy-aldehyde possessed very interesting odorous properties and that consequently it could present a utility as perfume ingredient in general.